GALLIUM ARSENIDE PIXEL AND MICROSTRIP DETECTORS

GALLIUM ARSENIDE (GAAS) SEMI-INSULATOR DETECTORS ARE KNOWN TO BE MORE RADIATION RESISTANT AND FASTER THAN SILICON (SI) SEMICONDUCTOR DETECTORS. IN THE "CURRENT MODE" OPERATION, THE SLOW COMPONENT, ATTRIBUTED TO HOLES, WAS FOUND TO BE DRASTICALLY REDUCED BY NEUTRON IRRADIATION OF THE CRYSTAL. IN FACT, THE GENERATED RECOMBINATION SITES REDUCE THE LEAKAGE CURRENT IN GAAS, IN STRIKING CONTRAST TO THE LEAKAGE CURRENT INCREASE IN SI CAUSED BY RADIATION DAMAGE. THE FAST ELECTRON COMPONENT IS NEARLY UNAFFECTED UP TO 10(15) NEUTRON/CM(2). IN THE "PARTICLE COUNTING MODE", CHARGE TRAPPING IN GAAS SURFACE BARRIER DETECTOR IS EXPECTED TO BE ELIMINATED BY NEUTRON IRRADIATION IN A SIMILAR FASHION. CURRENT SUPERCONDUCTING SUPER COLLIDER (SSC) CENTRAL TRACKERS ARE SI PIXEL AND MICROSTRIP DETECTORS. AT HIGH LUMINOSITIES (>10(33)/CM(2)S) SI DETECTORS CANNOT HANDLE THE HIGH COUNTING RATE AND CANNOT WITHSTAND THE LARGE DOSE (100 KGY, OR 3 X 10(14) PROTONS/CM(2)), BUT GAAS DETECTORS CAN BE MADE 10 TIMES FASTER AND ARE EXPECTED TO WORK BEYOND 100 KGY. IF THE RADIATION ENVIRONMENT IS SUCH THAT THE SI DETECTORS QUIT WORKING WITHIN A YEAR, THE GAAS DETECTORS ARE EXPECTED TO WORK BEYOND 10 YEARS, POSSIBLY OUTLASTING THE SSC LIFE, AND CAN ALSO HANDLE THE COUNTING RATE ADEQUATELY. IT IS THEREFORE IMPORTANT TO EXPLORE PIXEL AND MICROSTRIP DETECTORS BASED ON GAAS TECHNOLOGY. THE PLANNED GAAS PIXEL IS A PROTOTYPE HYBRID DETECTOR MADE BY JOINING THE INDEPENDENTLY FABRICATED, NEUTRON-TREATED SINGLE GAAS CELL (50 MUM X 150 MUM THICK) AND A COMPOSITE METAL OXIDE SEMICONDUCTOR INTEGRATED CIRCUIT BY A METALLIC BOND. IN PHASE I THE PIXEL WILL BE FABRICATED, THE DETECTION EFFICIENCY, CHARGE TRAPPING, RADIATION RESISTANCE, AND SPEED OF THIS DETECTOR WILL BE STUDIED, AND THE APPLICABILITY OF THE TECHNOLOGY TO MULTIPLE ARRAYS OF PIXEL AND MICROSTRIP DETECTORS WILL BE ASSESSED. VERY HIGH SPEED AND RADIATION HARD PIXEL AND MICROSTRIP DETECTORS ARE EXPECTED TO HAVE SIGNIFICANT COMMERCIAL APPLICATIONS.